I am using Civirm 5.1 on Joomla and using the GDPR extension to update Communication preferences. The org has only 1 public facing group with just 1 Mailing list - and the entire purpose of the communication is to ask people if they wish to sign up. If they do not repond they will be removed from Group and if they do respond it is ONLY for the purpose of asking to receive newsletter. Therefore, we need to make the Mailing Group compulsory to sign (as opposed to optional). We do not want form used if you do not want newsletter.

Thank you very much for this suggestion - it seems to work fine for me - I also changed text under Data Policy to indicate signing up to Newsletter.
– Andy GoodallMay 15 '18 at 22:33

It seems I spoke to soon - I created a new user with email - sent user test email - clicked sign up in email - completed remaining fields and clicked save - however, GDPR comm preferences not updated in contact and contact is NOT added to Group despite stating so in Advanced Profile.
– Andy GoodallMay 15 '18 at 22:51

If I do the above recomemendation but otherwise leave the Subscriptions to Groups ticked and the form works as expected and eners person into Group - If left unticked then contact will not be placed in group despite Advanced setting adding to Group.
– Andy GoodallMay 16 '18 at 6:40

The form is designed to be explicit consent i.e. supporters must tick the box for the group your going to add them to. We haven't tested them being automatically added to groups as its against GDPR guidelines however if you raise an issue on our extension issue queue we can take a look github.com/veda-consulting/uk.co.vedaconsulting.gdpr/issues.
– Parvez SalehMay 18 '18 at 10:02